Header size

[landracing]

Anybody have any good information on header size for turbo.
 
 What I am doing is building a header into a log exhaust manifold. So basically 4 - 1 3/8 pipes from head coming into a log manifold, then in the middle of the log manifold at bottom I am putting the turbo. At what point would the log manifold be to small or big.
 
 So I have 4- 1 3/8 pipes coming into a 2" Log exhaust manifold, at the bottom of the manifold I put a 2" pipe down about 1 3/4" and mounted the turbo on that. Being a 600cc motor with intentions to build 15 lbs of boost at what point will this be to restrictive? Or am I just thinking to hard on it and its fine the way it is.
 
 Should I increase the size of log to a 2 1/2"? Or will this larger diameter slow down the velocity of air into the turbo?
 
 Just thinking outloud.
 
 Jonathan

[ddahlgren]

Make the collector the same size as the turbine inlet in sq inches.
 
  <small>[ February 19, 2004, 05:02 AM: Message edited by: Dave Dahlgren ]</small>

[Ryan]

Jon,
 The '84 - '85 Kawasaki 750 turbo used a very small header tube to keep exhaust velocity high. Visit 750turbo.com there you can see pictures of the spider pipe and what mods some of us are doing to that engine. 206 horsepower with those tiny exhaust tubes, incredible. Makes no sence at all...
 
 Think 20+ pounds of boost my good man. Life begins at 30psi of boost.

[Jim McNaul]

One of the primary things I have experienced is to retain all the heat possible. Don't make the pipes any longer than you have to or with any more surface area than you have to. Have you noticed that they many times insulate the entire exhaust system on turbo installations. As exhaust cools it looses volume. It is the volume and the heat that spin the turbine. Look at the installations on turbocharged commercial engines. Very simple and compact. Believe me, the truckers and generator set and earthmoving people are just about as interested in performance and fuel economy as you are.